What women need to know about birth control

Blame it on squeamish American culture, but birth control methods and ladies’ hygiene products are often advertised with cutesie suggestion, capturing your attention with synchronized swimmers, for example, instead of driving home the details you need to know about the product. To get down to birth control basics, TIME turned to contraception expert Katharine O’Connell White, a practicing obstetrician and gynecologist at Baystate Medical Center in Springfield, Massachusetts, and a former assistant professor of obstetrics and gynecology at Columbia University Medical Center.

TIME: Descriptions of birth control pills’ effectiveness are always qualified by “when taken correctly.” What happens when patients don’t take the pill correctly, that is, forgetting one day or skipping a pill by accident, for example? What is the “real world” effectiveness of the birth control pill?

White: It is not human nature to take a pill every day when you feel well. Studies have shown that even doctors, who should definitely know what the problem is with not taking their medication, [aren’t great about doing it when they feel well]. To sum up those types of studies very broadly, about two thirds of doctors take their medications only two thirds of the time! Everybody else is worse. If you have a bladder infection, which is extremely uncomfortable, you’re going to take your antibiotics. If you have a sore throat, or you have strep, you’re going to take your pills. It’s a trigger, your body is telling you something is wrong and it triggers you to remember to take your pills. When you’re feeling well, it is not in human nature to always remember. It’s not that there aren’t perfect pill takers, there are. But what is much more normal is for every once in a while to forget to take a pill, because of a vacation, or any sort of disruption in routine—you move and the pack of pills gets lost or misplaced. You change jobs and have to change insurance, so now you have to wait for the new card to get the new pack. There are so many reasons that it can be difficult to take the pill.

With regard to what missing pills can do to effectiveness, if you miss one pill, the hormones are in your blood enough that when you take that pill late, or even the next day if you double up, so to speak, you’re not at increased risk for pregnancy. If you miss two, though, you are now at risk. Fortunately, there’s a little bit of a margin of error built in if you miss one pill, but missing more than one does put you at risk. So, what’s the real world effectiveness of the birth control pill if it’s 97% in theory? It’s about 92%.

TIME: Can taking the pill increase your risk for cancer?

White: People talk about hormones as being scary and unhealthy and unnatural. But if you want to look at what “natural” actually is, first of all, historically, “natural” is getting your period later than we all get it now—it’s getting your first period when you’re 14- or 15-years-old, and it’s going through menopause in your early 40s, and spending a good portion of the time in between either pregnant or breast feeding. Historically, women have not had 30 years of periods. Now, however, girls first get their period between 10- and 12-years-old, women go through menopause at 50, and they spend an average of maybe three years trying to get pregnant, being pregnant or breast feeding. That’s a lot of periods. Every time you go through a menstrual cycle and the cells in your ovaries react to the release of an egg and the lining of your uterus changes over, there’s a chance of an error happening that can lead to cancer. The way that the pill can help prevent that is that it basically puts your ovaries to sleep for a while. The pill can actually cut your risk for ovarian cancer by 50%, and your risk for uterine cancer by 80%. For people who have a family history of either of those two diseases, the best thing I can do for them as their doctor is to put them on the pill.

TIME: What about breast cancer? How can the pill impact your odds?

White: With regards to breast cancer, that’s a bit more complicated. To try to sum up, women who are diagnosed with breast cancer who have been on or who are on the pill tend to get diagnosed at earlier stages when the cancer is easier to treat. So what does that mean exactly? A lot of oncologists believe that the birth control pill acts as a promoter, meaning, that cancer was developing anyway, but the pill makes it happen faster, but because women on the pill are receiving regular medical care, it is also generally picked up sooner. That is in contrast to the pill being an initiator—meaning, it isn’t giving you cancer if you wouldn’t have had it anyway. Though, even after a lot of study, that relationship is still unclear. In my opinion, the potential small risk for breast cancer is far outweighed by the proven benefits in protection against ovarian or uterine cancer—overall it’s more of a cancer prevention drug. What’s more, with regard to cancer prevention, the longer you’re on the pill, the greater the protection.

TIME: There seems to be a common perception that, if you’ve been on the pill for years and years, but are now ready to try to conceive, you have to spend some time letting the hormones flush out of your system. Is there any truth to that?

White: Back to what we were saying earlier, that if you miss two pills you may ovulate that month—the pills are out of your system right away. That’s why it’s so unforgiving with regard to forgetting the pill. But the good thing is, when you are ready to try to get pregnant, once you stop taking the pill, it’s gone. Women don’t need to get off the pill three to six months before they’re trying to conceive, their bodies return to normal right away. The other thing about the fertility question is that you get people who have been on the pill for a very long time who are now trying to get pregnant in their late 30s, and they’re having trouble, they often think it must be the pill. Well, it’s harder to get pregnant in your late 30s than it is when you’re 21. Once you stop the pill, your fertility is going to return to what it would have been anyway—I know 45-year-olds with kids in college who have unplanned pregnancies, and I know 30-year-old patients who need donor eggs to have a baby.

TIME: How safe is it to take the “active” pills of birth control back to back, skipping the placebo pills—and possibly, your period?

White: Basically, the lining of your uterus doesn’t really build up on the birth control pill, but if you stop taking hormones, all of a sudden there will be some build up and then it’s going to shed, and that’s why you get bleeding. So if you don’t stop taking active pills, you won’t get build up. There are pills that are now designed especially for this—the Seasonale/Seasonique pills, where you get your period every few months, and Lybrel, with which you don’t get your period ever. In truth, these are just savvy marketers doing what doctors have been doing for years when a woman has a vacation or a honeymoon. You don’t have to be on one of those pills to do it though.

The best type of regular pills to use for this purpose are what’s called monophasic, and what that means is that there is the same amount of hormones in each pill. There are also biphasic pills that have two levels of hormones depending on where you are in the cycle, and then there are triphasic—which include pills like Ortho Tri-Cyclen. [You can tell the difference by how many different colored pills there are in your birth control pack. If they’re all the same, it’s monophasic. If there are three different colors, it’s triphasic.] If you try to take the biphasic or the triphasic pills back to back, that leads to much more break-through bleeding.

But breakthrough bleeding is definitely possible [regardless of which birth control pill you take]. The more packs of pills you go through like this, the more likely you are to see breakthrough bleeding, and that can range from a few days of spotting to bleeding on and off for a month. Every woman is different with regard to how her body responds to using continuous hormones. There’s no way to know how you will respond until you try it, and there’s no danger to [skipping placebo pills].(Though, I don’t mean to minimize just how annoying it is to be bleeding when you don’t expect to!)

TIME: What about other hormone-based birth control methods. Are they safe to use this way?

White: The ring you can very much use back to back, but the patch you actually can’t, because the doses of the patch are higher than those of the birth control pill, and you actually need to take a break once a month. The ring is actually a lower dose of hormones than birth control pills. The only problem with the ring is what I call unexpected or unnoticed expulsion. The ring is so comfortable to use, that if it comes out, you wouldn’t necessarily notice it was gone. So, I tell my patients to check once a week to make sure it’s still in the right place.

TIME: There are some people who complain about negative side effects from the pill—specifically that it can make you gain weight. Is that true?

White: Ignoring the first generation of pills, when they used to be higher dose, all modern birth control pills [from the last two decades or so] have been low dose and do not lead to weight gain. There are two big things that also tend to happen around the same time that people begin using birth control pills. First, when you’re a teenager, you’re going to gain weight. If you look at the normal growth curves for what adolescents look like from eighth grade through college and the way they gain weight, among girls who are on the pill and those who aren’t the curves are the same. Girls are all gaining weight, because developmentally that’s what you do when you’re a teenager—you’re getting boobs and hips, and so the scale goes up.

That is fairly well documented, but the other thing too is that, socially, a lot of women’s lives change when they’re in a committed relationship, which for many, is an initial reason to go on the pill. You may not get to the gym as much, you may go out to eat more, around the same time that you’re starting the pill, your lifestyle may shift, and that may lead to an extra few pounds. But it’s more related to what was changing in your life that made you go on the pill in the first place. There are a lot of reviews of well conducted studies that show that there’s no significant weight gain with the pill. There might be a few pounds of weight gain, that’s hard to tell precisely, but if you’re talking about five, 10 or 20 pounds, that’s not happening.

TIME: The pill has also been shown to improve acne. How does that work?

White: The hormones in the birth control pill increase the hormones in your body called sex hormone-binding globulin, and what that does is bind up testosterone. Women have testosterone, not nearly as much as men, but some. And it’s the hormone testosterone that leads to acne. So, this other hormone gets increased because of the birth control pill, and binds up the testosterone, decreasing acne. It’s as simple as that. (Additionally, the only thing that’s different about birth control pills marketed for their ability to fight acne, is that those were the marketers savvy enough to highlight it. All birth control pills do this.)

TIME: What about reduction in cramps, how does the pill help?

White: It’s actually chemicals called prostaglandins that are triggered by the ovulation cycle, and because you’re not letting any of that happen, the prostaglandins don’t get released either. That’s one of the main chain reactions that happens when you’re ovulating each month, and cutting those changes off at the pass reduces the pain-causing chemicals. In some cases, the pill can even get rid of cramps completely, though it depends on how severe they were to start with. In people who had really severe cramps to begin with, they likely won’t completely go away, but they should be reduced to a tolerable level. For women who had mild cramps, they can go away completely. That also means though, that when you go off the pill, your cramps will come back at their earlier intensity. It’s a rude awakening.

TIME: Are there any women who shouldn’t take the pill?

White: There is a list of contraindications, but briefly, women who have high blood pressure, migraine headaches with aura—which is when people have neurological symptoms such as changes in vision or hearing that precede their headaches, smokers over 35, women who have a personal history of blog clots. Specifically speaking to the issue of clots—does the birth control pill increase your risk of blood clots? Yes, it does. But it does not increase it anywhere near as much as pregnancy. If you’re a nun, then yes, your risk of clot will be higher, but if the alternative to the pill is possible pregnancy, then with that your risk is much higher than if you’re on the pill. Yes, the pill can increase your risk for blood clots, but that risk is still very low.

TIME: We’ve spoken quite a bit about hormone-based birth control, namely, the pill. But what about other types, such as the Intrauterine Device (IUD). Is it really making a comeback?

White: Our profession is trying really hard to bring it back the IUD, it’s the closest thing to perfect birth control that we have. There’s a lot of education that needs to happen, both for health care providers and patients, but yes, it’s coming back, which is a great thing. It’s not only the most effective birth control for your money—meaning it’s more than 99% effective—but it takes human error out of the equation, set it and forget it. You get the IUD implanted, and then you don’t have to think about it. If you travel, if you lose your insurance, if anything happens, you are still protected against pregnancy. Also, there are very few women who are contraindicated for the IUD, and there are two available, so virtually all women can use one or the other.

TIME: How do IUDs work?

White: The two IUDs work differently. The copper IUD (ParaGard) releases copper into the fluid in the lining of your uterus, and the copper is a really strong spermicide. The Mirena IUD thickens the mucus in the cervix making it harder for sperm to get up there, and it changes the lining of the uterus, making it harder for an egg to implant, and it changes the [ability for sperm to find their way to the egg], so it works on a lot of different levels to prevent pregnancy from happening.

TIME: Can using the IUD be dangerous at all? Are there any common complications?

White: There are some possible—and infrequent—complications, but then again, nothing in life is uncomplicated. The complications around insertion are infection in the few weeks after—whenever you have a surgical procedure that involves placing an instrument in the body, there’s always a risk of infection. And there’s also the risk of what’s called perforation, when a tiny hole is made in the uterus and the IUD then ends up in your belly, not in our uterus. It’s very rare, but not impossible. Those are the two possible complications around insertion.

But once it’s inserted well and you get past the window for infection, which is three weeks, the only other complication point is what’s called expulsion, meaning the body decides it doesn’t want the IUD anymore and tries to expel it. The thing about expulsion though is that, if your body is trying to get rid of the IUD, you’re going to know. You’re going to have a lot of pain or unusual bleeding or both, which means you need to go to your doctor to have it checked.

TIME: How does the IUD compare cost-wise to other methods?

White: If you look at the cost spread out over years, it’s one of the cheapest birth control methods, but it has a much higher up front cost than other methods. [The ring, patch and birth control pills all have a monthly cost ranging from about $20-$45.] The up-front cost for an IUD is between $500-$700, for the device itself, and the insertion. Some more points about the IUD: It’s safe to use even if you haven’t had a baby. It’s safe to use even if you’re a teenager. It’s the most effective reversible form of birth control, and the the IUD doesn’t increase your chances of an infection or infertility.

TIME: What about birth control shots?

White: Studies of Depo-Provera injections have shown that when you’re on Depo-Provera you can experience some bone loss, and those findings have made some providers hesitant to even give the method to teenagers at all, because they’re still growing, or to give it to any woman for longer than a couple of years. The evidence is far from clear as to what the long term ramifications are, one, because most women don’t use a birth control methods for 20 years straight. But even in certain parts of Asia where people do use the injection for 10, 15, 20 years, they don’t report an increased risk of breaking a hip at age 70. There’s a lot of hysteria now based on how bones look on x-ray, but that may be one of the problems with having too much technology and not knowing what to do with the result. The bone loss that people have due to Depo-Provera is similar to that of women breast feeding, and we would never recommend to women that they not breast feed.

TIME: On their own, how effective are condoms?

White: Condoms are not that great with regard to effectiveness, despite the idea that people have that they’re blocking the sperm from getting to the egg so they must be really effective. They have a 15% failure rate, and while 85% is not nothing, when you consider that the IUD is 99%, and hormonal methods are about 92-97%, it’s not as good at preventing pregnancy. But, unlike the hormonal methods or the IUD, condoms do help protect against sexually transmitted infections. They’re very good at that.

But condoms are not fool-proof in protecting against sexually transmitted infections, and particularly herpes and the human papillomavirus (HPV), which can both live in the outer genital skin. It’s not just penile and vaginal sex that can transmit STIs—what the sex-ed people call “outercourse” can be enough to transmit these viruses. Condoms do help reduce the risk, but they’re not 100%.

TIME: What is the safest way to have sex—specifically, to prevent both pregnancy and STDs?

White: I would say three things. For the safest sex possible, I would recommend an IUD to prevent pregnancy, condoms to prevent STDS, and one partner. One of the safest things you can do is to minimize the number of partners you have over a lifetime, so mutual monogamy.